NOVEL PROCESSING OF BORON CARBIDE (B 4 C): PLASMA SYNTHESIZED NANO POWDERS AND PRESSURELESS SINTERING FORMING OF COMPLEX SHAPES James Campbell, Melissa Klusewitz, Jerry LaSalvia, and Ernest Chin U.S. Army Research Laboratory Aberdeen Proving Ground, MD 21005-5069 Robert Speyer and Namtae Cho Georgia Institute of Technology Atlanta, GA 30332 Noel Vanier, Cheng-Hung Hung, Edward Abbott and Peter Votruba-Drzal PPG Industries 4325 Rosanna Drive Allison Park, Pennsylvania 15101 William Coblenz and Toni Marcheaux DARPA, Defense Sciences Office 3701 N. Fairfax Drive Arlington, VA 22203-1714 ABSTRACT Boron carbide, most often used in personnel armor systems, is rather difficult to form and is almost always densified from ceramic powders under heat and pressure. Recent developments by PPG and Georgia Tech are allowing for the full densification of nano-sized powders through a pressureless sintering route. PPG is manufacturing these powders in a plasma processing technique, and they are less expensive than traditionally produced powders. The powders are fonned directly in the plasma, and they can be doped with densification aids. Pressureless sintering teclmiques developed by Georgia Tech offers a low-cost processing route for B 4 C that was previously unavailable. Together both efforts will lead to boron carbide with shapes and sizes unavailable today and using a fine-grained domestically produced starting powder. I. INTRODUCTION Boron carbide is an important armor ceramic that is primarily used in personnel protection applications due to its very low density and its ability to defeat small anns threats. Boron carbide has a density of 2.5 glcm', compared to 3.2 glcm' for silicon carbide (SiC) and 3.9 gI em' for aluminum oxide (AI,O,). Traditionally, boron carbide (B,C) annor is manufactured through the hot pressing of ceramic powders, which requires the application of uniaxial pressure during the sintering (densification) process. This processing route allows for only very simple shapes to be fonned, such as flat plates or those with some curvature, such as a Small Arms Protective Insert (SAP I) plate. Until recently, it has been very difficult to densify this ceramic to full density via a pressureless sintering route. Sintering would give the ability to make components with much more complicated geometries, such as conformable body armor and helmet liners. Georgia Institute of Technology (GlT) has developed a sintering approach with a follow-on hot isostatic (gas) pressing (HIP) to produce pressureless sintered, additive-free, B,C components at full density. Currently, almost all B,C powders used in armor applications are imported due the high amounts of electricity required to manufacture the material. It is formed in an electric arc furnace as a large billet of material, which is then ground down into the powders used to make ceramic bodies. PPG offers an alternate approach to making the powders. The starting materials are reacted in a plasma and powders are formed directly. These powders are nano-sized and the process allows for the addition of sintering aids directly into the powder.
NOVEL PROCESSING OF BORON CARBIDE (B4C): PLASMA SYNTHESIZED NANO POWDERS AND PRESSURELESS SINTERING FORMING OF COMPLEX SHAPES
Jun 20, 2023
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